The SuperMac computers are entirely stable and compatible with Mac OS 8.1. As always, it is recommended that one check for updates to the software utilities that came with one's SuperMac computer before upgrading to a new OS version. Some specific test notes are included at the end of this advisory. Also, if you are upgrading to Mac OS 8.1 from Mac OS 7.6.1 or earlier, we strongly recommend that you read the Mac OS 8.0 Technical Report before making the upgrade to 8.1, as certain cautions which apply to Mac OS 8.0 also apply to Mac OS 8.1.
Regarding the new HFS+ Extended Format, there are a number of issues on which we must caution our customers. These issues pertain to any Mac OS computer.
In brief, we recommend that our customers not reformat their drives with the new HFS+ Extended Format unless and until they own a bootable Apple Mac OS 8.1 CD or an HFS+ compatible diagnostics CD, such as Micromat's TechTool Pro or Symantec's Norton Utilities. This is to ensure that users have a means of recovery should anything happen to the OS installation on their hard drive. Furthermore, J700, J710, S900, and S910 owners with E100 cards in those systems should be advised that the E100 software does not presently format drives in the HFS+ Extended Format. There is a workaround, but owners of these systems are advised not to use the HFS+ Extended Format on drives connected to the E100 card until reviewing the HFS+ info below. When E100 owners are ready to proceed, instructions for creating an HFS+ Extended Format volume with the E100 card can be found in KnowledgeBase record #KB00326.
The HFS+ Extended Format, available under Mac OS 8.1, represents a dramatically different implementation of the Macintosh filing system. Unfortunately, although HFS+ makes more efficient use of drive space, it is incompatible with versions of the Mac OS prior to 8.1. As a result, if you format your hard disk drive to use the HFS+ Extended Format, that drive will only be accessible under Mac OS 8.1 and later. The obvious implication of this are that unless and until you have a bootable Mac OS 8.1 CD (1) you will not be able to access that hard disk drive when booting from your UMAX/SuperMac System CD; (2) you may not be able to easily repair drive-related problems; (3) you will not be able to reinstall Mac OS 8.0 or older versions of the Mac OS without first reformatting the HFS+ drive; (4) you will not be able to reinstall Mac OS 8.1 without reformatting the drive, reinstalling Mac OS 8.0, and then reinstalling Mac OS 8.1 again.
Fortunately, even though one must use at least 8.1 to take advantage of HFS+, one does not need to use HFS+ to take advantage of 8.1. Therefore, the potential pitfalls described above can be avoided simply by installing the Mac OS 8.1 update -- either from an internet download of the 8.1 updater or via the 8.1 CD -- but not reformatting to use the HFS+ Extended Format.
Having the Mac OS 8.1 CD will afford one a means of booting under 8.1, accessing HFS+ boot drives, and, if necessary, reinstalling Mac OS 8.1 on that HFS+ drive. Since reinstalling the system software is an annoying but sometimes necessary maintenance procedure, the importance of having the Mac OS 8.1 CD should be clear. Further, Apple also recommends that one not use an HFS+ Extended Format volume as one's start up disk unless one has the Mac OS 8.1 CD.
The following results encompass Mac OS 8.1 compatibility with the software packages bundled with SuperMac computers. Software not bundled by Umax is beyond the scope of this report. Test systems were the C600x/280 (w/CacheDoubler) and S900 (multiple models & configurations).
TechTool Pro 1.0.5u
Norton Disk Doctor 3.5.1
CD-ROM Toolkit 2.3.2
Apple Multiprocessor HAL
The following have undergone cursory testing and did not exhibit any change in behavior:
The following have not been tested: